U.S. patent application number 10/885970 was filed with the patent office on 2005-03-03 for method for manufacturing stamper, stamper and optical recording medium.
Invention is credited to Kawaguchi, Yuuko, Tomiyama, Morio.
Application Number | 20050045481 10/885970 |
Document ID | / |
Family ID | 34101291 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050045481 |
Kind Code |
A1 |
Kawaguchi, Yuuko ; et
al. |
March 3, 2005 |
Method for manufacturing stamper, stamper and optical recording
medium
Abstract
When producing a second stamper by forming a nickel
electroformed film on a father stamper having patterns of pits and
lands, defects appear on the second stamper during the stage of
separating the second stamper from the father stamper. The object
of the present invention is to decrease these defects. A method for
manufacturing a stamper comprises performing a plasma surface
treatment on a surface of a father stamper 106 having patterns of
pits and lands, forming a nickel electroformed film (II) 107 on the
surface of the father stamper 106, and separating the nickel
electroformed film (II) 107 from the father stamper 106 so as to
form a mother stamper 108.
Inventors: |
Kawaguchi, Yuuko; (Ibaraki
city, JP) ; Tomiyama, Morio; (Ikoma city,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
34101291 |
Appl. No.: |
10/885970 |
Filed: |
July 8, 2004 |
Current U.S.
Class: |
205/67 ;
264/1.33; G9B/7.196 |
Current CPC
Class: |
C25D 1/22 20130101; G11B
7/263 20130101; B29D 17/005 20130101 |
Class at
Publication: |
205/067 ;
264/001.33 |
International
Class: |
B29D 017/00; C25D
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2003 |
JP |
2003-309174 |
Claims
What is claimed is:
1. A method for manufacturing a stamper, comprising the steps of:
performing plasma surface treatment on a surface of a father
stamper having patterns of pits and lands; forming a nickel
electroformed film on the surface of the father stamper; and
forming a second stamper by separating the nickel electroformed
film from the father stamper.
2. The method of claim 1, wherein at least Ar gas is used for the
plasma surface treatment.
3. The method of claim 1, wherein the electric power of a RF power
source for the plasma surface treatment is within a range between
50W and 500W.
4. The method of claim 2, wherein the electric power of a RF power
source for the plasma surface treatment is within a range between
50W and 500W.
5. The method of claim of 1, wherein a contact angle between the
surface of the father stamper and water on the surface of the
father stamper after the plasma surface treatment is smaller by 20
degrees or more compared to a contact angle between the surface of
the father stamper and water on the surface of the father stamper
before the plasma surface treatment.
6. The method of claim 2, wherein a contact angle between the
surface of the father stamper and water on the surface of the
father stamper after the plasma surface treatment is smaller by 20
degrees or more compared to a contact angle between the surface of
the father stamper and water on the surface of the father stamper
before the plasma surface treatment.
7. The method of claim 3, wherein a contact angle between the
surface of the father stamper and water on the surface of the
father stamper after the plasma surface treatment is smaller by 20
degrees or more compared to a contact angle between the surface of
the father stamper and water on the surface of the father stamper
before the plasma surface treatment.
8. The method of claim 1, further comprising the step of supplying
water to the surface of the father stamper after performing the
plasma surface treatment and before forming the electroformed
film.
9. The method of claim 8, wherein the water supply step begins
within 30 minutes after the plasma surface treatment.
10. The method of claim 8, wherein the water supply step is
performed by immersing the father stamper in water.
11. The method of claim 8, wherein the plasma surface treatment is
performed in a chamber, and the water supply step is performed by
introducing water vapor into the chamber.
12. The method of claim 1, further comprising the step of forming a
film mainly composed of nickel hydroxide on the surface of the
father stamper after performing the plasma surface treatment and
before forming the electroformed film.
13. A stamper produced by the manufacturing method of claim of
1.
14. An optical recording medium produced by the stamper of claim
13.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for manufacturing
a stamper for disk-shaped optical disks used to reproduce
information, a stamper, and an optical recording medium.
[0003] 2. Description of the Prior Art
[0004] Optical recording media that record and reproduce
information upon application of an optical beam are widely used,
and increases in recording density are expected in the future.
[0005] Recently, various optical disks have been developed which
can reproduce many images and large amounts of speech data and
digital data. Research has been directed toward making disks with a
higher recording density.
[0006] Conventional stampers which are used to form optical
recording media which record and reproduce information by optical
means such as an optical laser are known. An optical recording
media tracking groove, and patterns of pits and lands corresponding
to information pits and the like, are formed on the optical
recording media stamper. The optical recording media groove portion
is formed by transcribing the patterns of pits and lands to a
thermoplastic resin, for example, a polycarbonate resin.
[0007] FIG. 2 shows a conventional manufacturing process for a
stamper. As shown in the figure, in the conventional method, a
conductive film 204 is formed by performing a conductive process in
which nickel is sputtered on the surface of the patterns of pits
and lands 202 that are formed on a glass substrate 201 included in
a master disk 203 (FIG. 2A). After the process, an electroformed
film (I) 205 is formed by electroforming nickel on the conductive
film 204 (FIG. 2B). Next, the conductive film 204 and the
electroformed film (I) 205 are separated as a unitary member from
the master disk 203 so as to produce a father stamper 206 (FIG.
2C). In practice, because several substrates having patterns of
pits and lands will be produced, an electroformed film (II) 207 is
formed by performing electroforming on the surface of the father
stamper 206 (FIG. 2D). Then, a mother stamper 208 will be achieved
by separating the electroformed film (II) 207 from the father
stamper 206 (FIG. 2E). By applying a method such as injection
molding to the mother stamper 208, the substrate of an optical disk
210 can be mass produced. In the above-mentioned method of
manufacturing the stamper, nickel is used as a material for the
conductive film and the electroformed film.
[0008] One problem in the manufacturing process described above is
that, when separating the electroformed film (II) 207 from the
father stamper 206 during the electroforming process to form the
film (II) 207, the film (II) 207 may become integral with the
conductive film 204 and cannot be separated from each other. This
is because the electroformed film (II) 207 is formed by
electroforming nickel on the surface of the conductive film 204
which also contains nickel itself, and this means both the film
(II) 207 and the conductive film 204 are composed of the same
metal.
[0009] To resolve these problems, methods have been proposed such
as:
[0010] 1) applying an oxidation process using hypohalous acid to a
surface of the nickel film of the conductive film 204 (see Japanese
unexamined patent publication JP54-40239); and
[0011] 2) applying an oxygen plasma process to a surface of the
nickel film of the conductive film 204 (see Japanese unexamined
patent publication JP59-173288).
[0012] The two methods mentioned above include an oxidation process
on the surface of the nickel film, but the following problems
(1)-(4) will be produced thereby:
[0013] (1) The film formation rate of the electroformed film (II)
207 will be slow because of a decrease in the electrical
conductivity of the nickel film;
[0014] (2) If the surface of the nickel film is not formed
uniformly after the oxidation process, the thickness of a produced
stamper will vary because the film formation rate of the
electroformed film (II) 207 will fluctuate over the surface;
[0015] (3) When the electroformed film (II) 207 is separated from
the nickel film on the conductive film 204, a portion of the film
(II) 207 will remain on the surface of the nickel film as residue
because the surface of the nickel film is not formed uniformly
after the oxidation process; and
[0016] (4) Liquid waste of the oxidation process in problem (1)
will cause environmental problems.
SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to propose an
alternative method for the above-mentioned oxidation process, and
to provide a stamper manufacturing method which can reduce defects
on a stamper produced by separating a mother stamper from a father
stamper to a minimum.
[0018] A method for manufacturing a stamper according to the
present invention includes the steps of performing a plasma surface
treatment on a surface of a father stamper having patterns of pits
and lands, forming a nickel electroformed film on the surface of
the father stamper, and forming a second stamper by separating the
nickel electroformed film from the father stamper.
[0019] In this method, a nickel oxidation film on the surface of
the father stamper is eliminated by the plasma surface treatment,
and the flatness and smoothness of the surface of the father
stamper improves.
[0020] By using this father stamper having improved flatness and
smoothness when forming the electroformed film, the separability
between the father stamper and the electroformed film improves.
[0021] Preferably, Ar gas is used during the plasma surface
treatment, because using Ar gas resolves the conventional problems
caused by use of oxygen gas.
[0022] Preferably, electric power from a RF power source for the
plasma surface treatment is within a range between 50W and 500W. In
this range, surface roughness of the father stamper is reduced, and
as a result, the separability between the father stamper and the
electroformed film is improved.
[0023] A contact angle between the surface of the father stamper
106 and water on the surface thereof after performing the plasma
surface treatment is smaller by 20 degrees or more compared to the
contact angle before the plasma surface treatment. In this case,
surface roughness of the father stamper is reduced, and as a
result, the separability between the father stamper and the
electroformed film is improved.
[0024] The manufacturing process may also comprise the step of
supplying water to the surface of the father stamper after
performing the plasma surface treatment and before forming the
electroformed film. The water supply step begins within 30 minutes
after performing the plasma surface treatment. This is because it
is necessary to form a film of nickel hydroxide on the surface of
the father stamper before nickel oxide can be formed.
[0025] The water supply step is performed by immersing the father
stamper in water. In addition, the water supply may be performed by
slowly introducing vapor into the chamber in which the plasma
surface treatment is performed on the surface of the father
stamper.
[0026] The manufacturing process may also comprise forming a film
on the surface of the father stamper in which the main component is
nickel hydroxide. This film is made after performing the plasma
surface treatment, and before forming the electroformed film. This
is because the separability between the father stamper and the
electroformed film is improved by forming the nickel hydroxide
between the stamper and the film.
[0027] According to each of the above-mentioned manufacturing
methods, a stamper with fewer defects is produced.
[0028] Also, by using the stamper, an optical information medium
having a better signal property than that of a conventional medium
is produced.
[0029] As described above, by eliminating a nickel oxidation film
from the surface of a father stamper having patterns of pits and
lands, the separability between the father stamper and a mother
stamper formed by electroforming can be improved, thereby reducing
defects in the mother stamper.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a stamper manufacturing method according to the
present invention; and
[0031] FIG. 2 is a conventional stamper manufacturing method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Hereinafter, embodiments of the present invention will be
explained with reference to FIG. 1.
[0033] As shown in FIG. 1, the invention relates to a method for
manufacturing a stamper to produce an optical disk.
[0034] FIG. 1A shows a glass substrate 101 onto which a photoresist
is deposited. The process of forming the substrate 101 with the
photoresist will now be explained. First, the glass substrate 101,
having a diameter of 200 nm and a thickness of 6 mm and with its
surface polished, is set on a turn table of a spin coating device.
Then, by depositing a photoresist on the polished surface of the
glass substrate 101, a photoresist layer 109 is formed having a
thickness of about 28 .mu.m.
[0035] FIG. 1B shows a master disk 103 consisting of the glass
substrate 101 on which patterns of pits and lands 102 have been
formed by exposure and development processes. The process of
forming the master disk 103 will now be explained. Here, an optical
laser with 250 nm wavelength converged by an object lens is applied
to the photoresist layer 109, and a groove having a track pitch of
0.32 .mu.m and a width of 0.15 .mu.m is formed on the area of the
photoresist layer 109 that is exposed to the laser (herein called
the exposed area). The glass substrate 101 and the photoresist
layer 109 including the exposed area is transferred to a
development device. Then, the photoresist layer 109 is developed
using a developing solution, and the solution is washed away with
purified water. Here, only the exposed area of the photoresist
layer 109 is eliminated during the exposure process, and the
non-exposed area of the photoresist layer 109 remains. The glass
substrate 101 has only the non-exposed area after the development
process and the desired pattern of pits and lands on the father
stamper 106 is eliminated. The process described above is an
example of using a positive photoresist, however, a negative
photoresist may also be available.
[0036] FIG. 1C shows the master disk 103 with a conductive film
104. The process of forming the conductive film 104 on the master
disk 103 will now be explained. The nickel conductive film 104 is
formed to a thickness of 20 nm on the master disk 103 using a
sputtering method.
[0037] FIG. 1D shows the master disk 103 on which an electroformed
film (I) 105 is electroformed. The process of electroforming will
now be explained. Here, the glass substrate 101 having the
conductive film 104 is set on a negative electrode system of a
electroforming device (not shown) and then, the nickel
electroforming is performed on the surface of the conductive film
104. In this way, the electroformed film (I) 105 in which the
patterns of pits and lands 102 have been transcribed is formed.
[0038] When the electroformed film (I) 105 has a thickness of 0.3
mm, the nickel electroforming is finished and the glass substrate
101 is detached from the negative electrode system of the
electroforming device. Then, the electroformed film (I) 105 and the
conductive film 104 are separated from the master disk 103 in a
unitary state so as to produce a father stamper 106. Note that the
contact angle between the surface of the father stamper 106 (i.e.
the side of the father stamper 106 having the surface of the
conductive film 104) and water on the surface thereof will be
measured before performing an etching step (described later) using
a measuring instrument for the contact angle, and the result should
be recorded (the contact angle may be 50 degrees, for example).
[0039] FIG. 1E shows the process of eliminating the nickel
oxidation film by performing the plasma surface treatment on the
surface of the father stamper 106 (the side of the surface of the
conductive film 104). Here, the father stamper 106 is inserted in a
parallel plate etching device (not shown), and the device is
evacuated using a cryopump or the like. At this time, assume the
ultimate vacuum is 3.times.10.sup.-4 (Pa). Note that it is
preferable for the ultimate vacuum before introducing etching gas
to be 1.times.10.sup.-3 (Pa) or below. After that, while pumping Ar
as the etching gas into the device at the flow rate of 100 sccm, a
vacuum exhaust is performed, and the pressure inside of the device
is maintained at 10 (Pa). Then, the voltage is increased to 100W,
and the etching is performed for 90 sec. Three minutes after the
etching, the father stamper 106 is rinsed with purified water for
five minutes. At this time, in the same way as described above, a
contact angle between the surface of the father stamper 106 and
water on the surface thereof is measured using a measuring
instrument for the contact angle. Here, assume the contact angle
between the surface of the father stamper and water on the surface
thereof is decreased by 20 degrees or more after etching has been
performed. For example, when the contact angle before the etching
is 50 degrees, the angle after the etching may be adjusted to 15
degrees. When the stamper is immersed in purified water within 30
minutes after performing the plasma surface treatment, a film in
which the main component thereof is nickel hydroxide is formed
uniformly on the surface of the father stamper 106.
[0040] FIG. 1F shows the father stamper 106 on which a film (II)
107 is electroformed. The process of forming the electroformed film
(II) 107 will now be explained. Here, the father stamper 106 after
the etching is set on a negative electrode system of an
electroforming device and then, the electroformed film (II) 107 is
formed (the process of forming an electroformed film). When the
electroformed film (II) 107 has a thickness of 0.3 mm, the nickel
electroforming is finished and the glass substrate 101 is detached
from the negative electrode system included in the electroforming
device. Next, the electroformed film (II) 107 is separated from the
father stamper 106 (the separation process).
[0041] According to the embodiments described above, the film (II)
107 can be cleanly separated from the father stamper 106 so as to
produce a mother stamper 108 (FIG. 1G) without defects or residue.
Further, from this mother stamper 108, optical recording media such
as an optical disk 110 is produced using an injection molding
machine.
[0042] Note that as shown in FIG. 1F, if the electroformed film
(II) 107 is formed on the conductive film 104, metallic bonds occur
because both the film 104 and the film (II) 107 are nickel metal.
However, as shown in FIG. 1G, in order to produce the mother
stamper 108, the electroformed film (II) 107 must be separated from
the conductive film 104.
[0043] As mentioned above, by applying the etching on the father
stamper using Ar gas, the improvement in separability between the
father stamper and the mother stamper is confirmed. The reason for
the improvement is thought to be as described below.
[0044] It is clear from performing a component analysis that if a
father stamper is exposed to the atmosphere after forming a nickel
conductive film, both nickel oxide and nickel hydroxide will be
formed on the surface of the conductive film. Because there is
little nickel oxide and nickel hydroxide produced with the
atmosphere, a method has been proposed in Japanese unexamined
patent publication JP59-173288 that forms nickel oxide on the
conductive film by performing ashing by actively using oxygen.
However, usually after performing the method, other processes are
performed such as a cleaning process using purified water, and a
process of immersing the father stamper in a solution like nickel
sulfamate in order to form the nickel electroformed film. Because
of these processes, the nickel hydroxide is usually formed on the
father stamper. Forming the nickel hydroxide is easily affected by
factors such as humidity of the atmosphere, and leaving the father
stamper in the atmosphere, resulting in the nickel hydroxide not
being formed uniformly on the father stamper.
[0045] As mentioned above, the ratio of nickel oxide to nickel
hydroxide on the father stamper is locally different, and the
separability between the two is different. Therefore, the
separability between the electroformed film (II) and the conductive
film becomes irregular, which may cause defects on the mother
stamper.
[0046] In the present invention, by performing the plasma surface
treatment on the surface of the father stamper (the side of the
surface of the conductive film 104), it is possible to eliminate
the nickel oxide and the nickel hydroxide formed on the surface.
Because the plasma surface treatment is performed in a vacuum, pure
nickel is exposed on the surface by eliminating the nickel oxide
and the nickel hydroxide. It is thought that by immersing the
father stamper 106 in purified water within 30 minutes after the
plasma surface treatment, the nickel hydroxide can be formed
uniformly on the surface.
[0047] Moreover, as described later, it is known that
hydrophilicity on the surface of the father stamper 106 improves by
performing a plasma surface treatment.
[0048] However, the improvement cannot be confirmed using devices
such as a surface measuring instrument or an interatomic force
microscope that can analyze the surface roughness by quantitative
analysis, because the plasma surface treatment is performed under
low energy conditions.
[0049] In contrast, the difference with or without the plasma
surface treatment can be quantitatively measured by examining
differences of contact angles with respect to water. In this case,
the contact angle between the surface of the father stamper 106 and
water on the surface thereof after performing the plasma surface
treatment is decreased by 20 degrees or more compared to the
contact angle before the treatment. The phenomenon in which the
contact angle with respect to water becomes smaller indicates that
the surface roughness of the father stamper 106 is improved.
Therefore, a contact area of the father stamper 106 and the
electroformed film (II) 107 can be smaller when electroforming
after plasma surface treatment, with an improvement in flatness and
smoothness, compared to that before the plasma surface treatment.
Thus, the separation performance between the father stamper 106 and
the electroforming film (II) 107 may also improve even due to the
effect of reducing the contact area.
[0050] As mentioned before, by etching the surface of the father
stamper 106 by plasma surface treatment, the separability between
the father stamper 106 and the electroformed film (II) 107 can be
improved. It is found that this phenomenon depends on the input
power of the etching as explained later. If the input power of the
etching is too large, the surface roughness becomes worse. This
surface roughness affects the quality of the mother stamper 108.
With an optical disk employing a substrate having patterns of pits
and lands which is produced from a stamper with such high surface
roughness, C/N (carrier to noise ratio) becomes worse because the
noise of the reproducing signal component increases during
reproduction. On the contrary, if the input power of the etching is
too small, the electroformed film (II) 107 cannot be separated from
the father stamper 106, because improvement in flatness and
smoothness by performing the plasma surface treatment cannot be
expected.
EXAMPLE 1
[0051] (1)
[0052] Experiments used to ascertain the etching conditions will be
described with regard to examination of the dependence of input
power during etching. Note that because time dependence during the
etching is not important, it is assumed to be constant at 90
seconds.
[0053] The results are shown in Table 1.
1TABLE 1 Input Power of the Noise Etching (W) Separability (dBm) 10
Bad N/A 30 Bad N/A 50 Good -71 200 Good -73 500 Good -72 600 Good
-68 800 Good -65 1000 Good -58
[0054] In Table 1, the term "Bad" in the separability column
indicates etching conditions in which the electroformed film (II)
107 could not be separated from the father stamper 106, or
conditions in which defects were produced on the electroformed film
(II) 107. The term "Good" in the same column indicates conditions
in which a mother stamper 108 without defects was produced.
[0055] In addition, the mother stamper 108 is set on an injection
molding machine, and then a substrate for an optical recording
medium with a thickness of 1.1 mm is produced by transcribing
patterns of the mother stamper 108 to a polycarbonate resin. The
surface roughness of the mother stamper 108 is measured as noise on
the optical information medium after transcription to the
polycarbonate substrate, and thus it is necessary to measure the
level of noise of the polycarbonate substrate. An aluminum
reflection film is formed to a thickness of 20 nm on the
information area side on the polycarbonate substrate, and further,
a sheet containing polycarbonate with a thickness of 0.1 mm is
formed on the reflection film. The substrate is set on an
information reproducing device, and the level of noise is measured.
In this information reproducing device, an optical system is used
which employs a wavelength of 405 nm and an object lens with a
numerical aperture of 0.85. Light for reproducing information is
applied to the substrate from the side of the polycarbonate sheet
with a thickness of 0.1 mm. By rotating the optical information
medium with a linear velocity of 5.0 m/s, the output signal is set
into a spectral analyzer and the level of noise in the 3 MHz
broadband was investigated. In this zone, when the level of noise
is -70 dBm or below, the noise does not affect the reproducing
signals. Therefore, to judge the surface properties, it is
preferable that the noise is -70 dBm or below. From this
examination, input power of the etching should be within the range
of 50W and 500W.
[0056] (2)
[0057] To investigate the change of flatness and smoothness of the
surface before and after etching, the contact angle between the
father stamper 106 and water on the surface thereof is measured
before and after etching, using a contact angle measurement
instrument. From the results, it was found that, before and after
etching, as the angle changed, the separability of the
electroformed film (II) 107 depends largely on the contact angle
with respect to water on the surface of the father stamper 106. On
the other hand, because the contact angle with respect to water on
the surface of the father stamper 106 can be controlled by
manipulating the pressure of Ar gas and voltage applied when
performing the etching, stampers were prepared that have different
contact angles with respect to water on the surface of the father
stamper 106 before and after etching. Then the relation between the
change of the contact angle before and after etching and the
electroformed film (II) 107 was investigated. The results are shown
in Table 2.
2 TABLE 2 Difference of Contact Angle before and after Etching
Separability 0 Bad 5 Bad 10 Bad 15 Bad 20 Good 25 Good 30 Good
[0058] Similar to Table 1, the separability column shows the
separability of the electroformed film (II) 107 and the existence
of defects. From the results, a decrease in the degree of the
contact angle with respect to water on the surface of the father
stamper 106 should be 20 degrees or more.
EXAMPLE 2
[0059] (1)
[0060] In Example 2, a mother stamper 108 will be formed via the
same steps and procedures as described above. FIG. 1 will be used
to describe this.
[0061] It is thought that there is a relationship between the
separability of the mother stamper 108 and the existence of defects
on the stamper and whether it is possible to form nickel hydroxide
uniformly on the father stamper 106. To form the hydroxide
uniformly on the stamper, the stamper needs to be immersed in water
quickly after the plasma surface treatment. On the contrary, after
the treatment, if the father stamper 106 is left in the atmosphere,
both nickel oxide and nickel hydroxide are produced. Because the
ratios of nickel oxide to nickel hydroxide are different locally,
and the separabilities of these materials are also different, then
the difference of the separability may occur locally and the
possibility of defects remaining on the mother stamper 108
increases.
[0062] In Table 3, the relationship between the time that the
father stamper 106 is left in the atmosphere after the plasma
surface treatment and the existence of defects (separability) on
the mother stamper 108 is described.
3 TABLE 3 Time Left in Atmosphere (min.) Separability 1 Good 10
Good 20 Good 30 Good 31 Bad 40 Bad
[0063] When performing the plasma surface treatment on the father
stamper 106, nickel oxide and nickel hydroxide are eliminated and
pure nickel is exposed. Therefore, if the father stamper 106 with
pure nickel on the surface is left in the atmosphere for over 30
minutes, both nickel oxide and nickel hydroxide are formed, then
residue will be produced on the mother stamper 108 and the defects
will remain on the surface during the separation process, because
the separability is not uniform. Therefore, it is preferable that
the time that the father stamper 106 is left in the atmosphere
after the plasma surface treatment is 30 minutes or less.
[0064] (2)
[0065] In this example, the mother stamper 108 was formed using the
same process as described above, without immersing the stamper in
purified water after the plasma surface treatment. Instead of the
immersing process, the pressure inside the chamber used for the
plasma surface treatment of the father stamper 106 is returned to
atmospheric pressure by applying vapor after the plasma surface
treatment. According to this process, on the surface of the father
stamper 106, nickel hydroxide of very high purity is formed. Note
that it is also preferable that the process is performed within 30
minutes after the plasma treatment.
[0066] The method for manufacturing a stamper of this invention is
useful as a stamper production method for optical recording media
and the like. In addition, it may be applied to a manufacturing
method of a stamper produced by electroforming.
* * * * *